docs: def _draw_line_numbers(self):
          """
          Create drawables for the line numbers.
          """
          if not self.line_numbers:
              return
          for p in xrange(self.maxlineno):
              n = p + self.line_number_start
              if (n % self.line_number_step) == 0:
                  self._draw_linenumber(p, n)